Growth and development of finishing pigs in bedded hoop and confinement buildings during summer and winter was evaluated using serial ultrasound measurements and weighing. A summer trial and a winter trial were conducted. Pigs were housed in a hoop finishing building (9.1 x 18.3 m) designed to hold 150 pigs or a mechanically ventilated, totally slatted confinement building with six pens holding 22 pigs per pen. Forty-eight pigs from the hoop building and eight pigs from each of the six pens in the confinement building were randomly selected and weighed and ultrasound images recorded every 14 d during the last 56 d of the finishing phase. Backfat (BF) accretion rates were greater for summer hoop pigs (SH) than summer confinement pigs (SC) at 80 kg, and at 90 kg (P < 0.05), but did not differ at 95 to 115 kg. In winter, BF accretion rates did not differ from 80 to 105 kg, but winter hoop pigs (WH) had less BF accretion than winter confinement pigs (WC) at 110 kg and 115 kg (P < 0.05). Loin muscle (LM) accretion rates did not differ at 80 and 85 kg or from 100 to 115 kg, but were less for SH than SC at 90 kg and at 95 kg (P < 0.001). WH had greater LM accretion rates than WC from 80 to 115 kg (P < 0.05). Bodyweight gain (BWG) did not differ between SH and SC from 80 to 95 kg and was greater for SH from 100 to 115 kg (P < 0.05). Bodyweight gain did not differ for WH and WC pigs from 100 to 115 kg, but was less for WH than WC from 80 to 90 kg ( P < 0.001), and 95 kg (P < 0.05). These results indicate that performance of finishing pigs is dependent on thermal environment, and that hoop-reared pigs (particularly in winter) may compensate for a lag in performance early in the finishing period with greater accretion rates of LM and BW and lower accretion rates of BF later in the finishing period.